Double acting hydraulic servo governor



1964 J. H. PARKS ET AL 3,145,624

DOUBLE ACTING HYDRAULIC SERVO GOVERNOR Filed Sept. 29, 1961 INVENTORSJohn H. Parks BY John G. Wellwood TTORNEYS United States Patent Office3,145,624 Patented Aug. 25, 1964 3,145,624 DOUBLE ACTING HYDRAULIC SERVOGOVERNOR John H. Parks, Peoria, and John G. Wellwood, Pekin, Ill.,

assignors to Caterpillar Tractor Co., Peoria, Ill., a corporation ofCalifornia Filed Sept. 29, 1961, Ser. No. 141,857 1 Claim. (Cl. 91-366)The present invention relates to governors for controlling engine speedand more particularly to an engine speed governor having a hydraulicbooster.

Conventional governors utilized to control engine speeds generallyoperate through the interaction of flyweights and an opposing governorspring. The flyweights are mounted on a member which rotates at a speedproportional to the engine speed. The flyweights assume a positionconsistent with the centrifugal force supplied by the rotating member,and thereby determine the position of a fuel control member such as afuel pump rack bar. When the rack bar is positioned to supply fuel tothe engine to operate it at a speed which rotates the flyweights withsuflicient centrifugal force to counteract the opposing governor spring,constant speed operation is obtained. Adjustment of the governor spring,therefore, obtains a selected operating speed.

The high speeds at which modern engines often operate, poses aparticular problem with conventional governors. The flyweights whichmust be of a suflicient weight to operate the rack bar when low enginespeed is desired exert great forces against the opposing governor springwhen the engine is alternately operated at high speeds. It becomesnecessary to employ a governor spring capable of exerting high counterbalance forces, and such springs necessarily have high resistance todistortion. It has been found in practice that springs having suflicientresistance to properly operate the governor at high engine speeds areexceptionally difiicult to adjust when a variation in operating speed isdesired. It thus becomes desirable to provide a governor which furnishesaccurate control at both high and low engine speeds with the use oflight flyweights, thereby enabling a governor opposing spring ofmoderate resistance to be used.

Accordingly, it is an object of the present invention to provide animproved hydraulic servo system to be used in an engine speed governor.

It is another object of the present invention to provide a hydraulicservo system which enables the use of light flyweights and an opposingspring of moderate resilience in a governor capable of accuratelycontrolling the speed of an engine over a large range of speeds.

Further and more specific objects and advantages of the invention aremade apparent in the following specification wherein a preferred form ofthe invention is described by reference to the accompanying drawing.

The drawing is a side elevation sectional view of the governor of thepresent invention with parts broken away.

Referring to the drawing, the governor of the present invention isillustrated as comprising flyweights 11 pivotally mounted in a carrier12 as by pins 13. Carrier 12 is toothed as at 12a to provide a pinion inconstant mesh with a drive gear 14 secured to a shaft 16 forming a partof the timing gear train of an engine. Governor housing and a fuel pumphousing secured thereto form an enclosure in which the various parts ofthe invention reside.

Flyweights 11 move radially under the influence of changing engine speedto move a thrust member 17 against the opposing force of a governorspring 18. This axial movement of member 17 urges the fuel controlmember or engine rack bar 19 through an intermediate hydraulic servosystem generally indicated at 21. Servo system 21 includes a portedpiston 22 having a piston head 23 slidable in a cylinder 24 and a pistonbody of reduced diameter slidably maintained within a fixed sleeve 26. Avalve spool 28 is slidably maintained within a central bore 29 of piston22. A valve spool 28 is connected to an adaptor 31 by means of aconnecting rod 32 which is afiixed to the adaptor 31 as by a pin 33.Adaptor 31 engages thrust member 17 and serves as one of the seats forgovernor spring 18. The other end of spring 18 engages spring seat 34which is adjustably positioned by means of a lever 36. Adjustment oflever 36 by manually actuated linkage (not shown) varies the position ofseat 34 to adjust the opposing force of spring 18 as desired. Axiallyaligned with the rod 32 is a control rod 30 slidably journalled within ahollow bearing support 35 pressed into the governor housing 10 as shown.Spring seat 34 is slidably carried on the bearing 35. A contact plate 40secured to the end of rod 30 engages lever 36 upon clockwise rotationthereof. Spring blade 40a prevents damage to plate 40 through contactwith housing 10. The manner of operation of lever 36, plate 40, rod 30and a cam surface 45, is fully described in Patent No. 2,961,229, issuedNovember 22, 1960, to I. H. Parks for a Centrifugal Governor.

Increased speed of the engine will induce flyweights 11 to moveoutwardly and thereby urge adaptor 31 to the left, as shown in thedrawing, against the opposing force of spring 18. Valve spool 28 whichis connected to adaptor 31 will also move to the left. Spool 28 willmove relative to piston 22 and thereby align a recessed area orcircumscribing groove 41 in valve spool 28 with an opposing groove 42 inpiston 22. A supply of hydraulic fluid as from the engine lubricatingoil system (not shown) is supplied to the servo system 21 through intakeline 43 which communicates with the piston head 23 through a space 44between cylinder 24 and sleeve 26. An O-ring 46 forms a seal betweenfuel pump housing 15 and sleeve 26 to prevent the leakage of oil.Recessed portion 41 of spool 28 communicates with a central bore 49 inthe spool which opens into an area 51 containing a flange 37 on thespool. Oil accumulated in area 51 is free to pass therefrom through acentral bore 52 in rack bar 19 which, in turn, empties into the fuelpump housing which communicates with a supply reservoir, in this casethe engine crank case.

The alignment of groove 41 with groove 42 provides a path betweenchamber 40 in cylinder 24 and the central bore of spool 28 throughpiston port 53. Hydraulic fluid under pressure in chamber 40 is thenfree to be discharged therefrom allowing the hydraulic pressure on theother side of piston head 23 to urge piston 22 to the left. The leftwardmovement of piston 22 in response to the hydraulic pressure causesmovement of rack bar 19 and adjustment of fuel pumps 39 (one of which isshown). This leftward movement of piston 22 is relative to spool 28causing misalignment of groove 42 and recess 41 so as to discontinuecommunications therebetween. The over-all result of increased enginespeed is a leftward movement of rack bar 19 with the aid of servo system21 to reduce the amount of fuel metered to the engine to compensate forchange of load, and thereby restore the engine to operation at aconstant predetermined speed.

When flyweights 11 move inwardly due to a decrease in engine speed theforce from the flyweights against thrust member 17 is reduced allowingspring 18 to urge adaptor 31 to the right carrying with it spool 28.Spool 28, displaced to the right relative to the piston 22, establishescommunication between a groove 54 in the spool and groove 42 in piston22. This communication completes a path between the hydraulic input line43 and the chamber 40 through area 44, port 56 in piston 22, recess 54and port 53. The hydraulic fluid then admitted into chamber 40 creates aforce on the left side of the piston greater than that on the right sidemoving the piston and rack bar 19 to the rightto increase the fuelmetered from fuel pumps'39 to theengine. As piston 2 2moves to the.right the communication between recess 54 and recess- 42is obstructeddue to the relative motion be tween the piston and spool -valve 28bringing the servo 'to rest afterthe engine has re-established itsoperating speed.

imeans of the flanged end 37 .of spool 28 engaging piston '22, and tothe right by'the direct contact 'of spool 28 with rack bar 19.

Whatis claimed is:

In an engine governor for controlling the position of a fuel controlmember and having rotatable flyweights opposed by a spring, comprisingin combination:

"hydraulic servo means operatively disposed between thefiyweights andthe fuel 'controlmember Wherebythe flyweights do'not "operate thefuelcontrol member directly except when there is a loss of "hydraulicfiuid pressure, said servo means including;

a cylinder disposed coaxially with the axis of rotation of theflyweights; a piston reciprocably 'rno'u'nted in'the cylinder andconnected with the'fuelcontrol member, said piston having an axial boreextending therethrough and valve ports therein; valve spool slidablydisposed in the bore of said piston, said spool extending beyond the endof the axial bore adjacent the fuel control member, the portion of spoolextending out of the bore having a flange thereon wherein the flange islarger in diameter thanjthe' boreys'aid flanged end abutting the controlmember when said spool is urged toward the control member relative tosaid piston; means connecting said spool for adjustment by saidflyweights and spring such that movement of said fly'weights outwardlyurges said spool in one direction while movement inwardly urges saidspool in the other direction; a sourceof fluid under pressure incommunication with oneside of 'said'pi'ston; and co-acting v'alvingelements betweenthe spool and the piston for communicating the fluidsource with the other side ofsaidpiston in response to movement ofthe'spo'ol' inone direction and communicating a fluid reservoir" with theother side of said piston in 'responseto movement of said spool in theother direction.

References Cited in the file of this patent UNITED STATES PATENTS 7l5,961 Bouvier Dec. 16, 1902 2,106,684 Ring et'al. Jan. 25, 19382,197,743 Crafts et al. 'Apr. 16,1940 1,373,684 Holloway "Apr. 17, 19 452,446 l49 Wells July 27, 1948 12,721,072 Zuhn et a1. Oct. 18, 1955"2,928,378 Leduc Mar. 15, 1960

